Recently, semiconductor devices have been used for high-speed switching under a large amount of current. If such a semiconductor device is heated to a high temperature, its switching function may be influenced. For this reason, on the occasion of mounting a semiconductor device, a flow passage member having a flow passage capable of cooling the semiconductor device by heat exchange with a fluid is used.
As such a flow passage member, for example, in Patent Literature 1, it has been proposed a flow passage member in which a gap portion is formed as a refrigerant flow passage below a circuit for mounting a semiconductor component, and a distance t from the circuit to the gap portion in a thickness direction of a substrate satisfies a condition of 0.5 mm≤t≤5 mm, and the distance t and a width Y of the gap portion have a relation of Y≤20t.